mq: don't allow patches with some reserved names

The current list of reserved names includes only mq control files.

Also, reserve names starting with ".hg" (to avoid troubles with
e.g. .hgignore and .hgtags), and with ".mq" (to allow future
extensions).

This should fix issue841.

hgext/mq.py

@@ -600,9 +600,17 b' class queue:'
                     raise util.Abort(_("local changes found"))
         return m, a, r, d
 
+    _reserved = ('series', 'status', 'guards')
+    def check_reserved_name(self, name):
+        if (name in self._reserved or name.startswith('.hg')
+            or name.startswith('.mq')):
+            raise util.Abort(_('"%s" cannot be used as the name of a patch')
+                             % name)
+
     def new(self, repo, patch, *pats, **opts):
         msg = opts.get('msg')
         force = opts.get('force')
+        self.check_reserved_name(patch)
         if os.path.exists(self.join(patch)):
             raise util.Abort(_('patch "%s" already exists') % patch)
         if opts.get('include') or opts.get('exclude') or pats:
@@ -1372,6 +1380,7 b' class queue:'
 
                 if not patchname:
                     patchname = normname('%d.diff' % r)
+                self.check_reserved_name(patchname)
                 checkseries(patchname)
                 checkfile(patchname)
                 self.full_series.insert(0, patchname)
@@ -1394,6 +1403,7 b' class queue:'
                     raise util.Abort(_('-e is incompatible with import from -'))
                 if not patchname:
                     patchname = normname(filename)
+                self.check_reserved_name(patchname)
                 if not os.path.isfile(self.join(patchname)):
                     raise util.Abort(_("patch %s does not exist") % patchname)
             else:
@@ -1408,6 +1418,7 b' class queue:'
                     raise util.Abort(_("unable to read %s") % patchname)
                 if not patchname:
                     patchname = normname(os.path.basename(filename))
+                self.check_reserved_name(patchname)
                 checkfile(patchname)
                 patchf = self.opener(patchname, "w")
                 patchf.write(text)

tests/test-mq

@@ -42,6 +42,12 b' echo % qinit -c'
 hg --cwd c qinit -c
 hg -R c/.hg/patches st
 
+echo % qnew should refuse bad patch names
+hg -R c qnew series
+hg -R c qnew status
+hg -R c qnew guards
+hg -R c qnew .hgignore
+
 echo % qnew implies add
 
 hg -R c qnew test.patch

tests/test-mq.out

@@ -59,6 +59,11 b' adding b/z'
 % qinit -c
 A .hgignore
 A series
+% qnew should refuse bad patch names
+abort: "series" cannot be used as the name of a patch
+abort: "status" cannot be used as the name of a patch
+abort: "guards" cannot be used as the name of a patch
+abort: ".hgignore" cannot be used as the name of a patch
 % qnew implies add
 A .hgignore
 A series